In situ fabrication of a rose-shaped Co2P2O7/C nanohybrid via a coordination polymer template for supercapacitor application

Abstract

Herein, we report the construction of a rose-shaped cobalt phenylphosphonate coordination polymer [Co(PhPO₃)] via the solvothermal method, which has been used as a precursor to prepare porous Co₂P₂O₇/C nanohybrid through a thermal transformation process in N₂. By controlling the calcination temperature, a series of polyporous rose-shaped Co₂P₂O₇/C-X (X = 600, 700, 800, 900 and 1000) have been successfully obtained. The prepared Co₂P₂O₇/C-X materials present in situ hybrid nanostructures and a unique polyporous structure, which will provide rich electrochemical active centers and enough migration paths for electrons and electrolyte for fast and deep faradaic reactions. As a supercapacitor electrode, the optimized Co₂P₂O₇/C-900 demonstrated a specific capacitance of 349.6 F g⁻¹ at 1 A g⁻¹ and remarkable cycling performances (97.33% retention after 3000 cycles at 2 A g⁻¹). Moreover, using the porous rose-shaped Co₂P₂O₇/C-900 as a cathode with 3D porous graphene gel (3DPG) as an anode, an asymmetric supercapacitor Co₂P₂O₇/C-900//3DPG was fabricated. The device showed an energy density of 21.9 W h kg⁻¹ at a power density of 0.375 kW kg⁻¹ and outstanding cycle stability of maintaining 106.25% initial capacity after 10 000 cycles at 3 A g⁻¹.